Coupled experimental study and thermodynamic modeling of the Al2O3-Ti2O3-TiO2 system

Abstract

A complete critical evaluation and re-optimization of phase diagrams and thermodynamic properties of the Al2O3-Ti2O3-TiO2 system at 1 atm pressure has been performed. Equilibration and quenching experiment in the Al2O3-TiO2 system in air was also performed to constrain the solubility limit of Al2O3 in TiO2 rutile solution at high temperatures. The molten oxide phase was described by the Modified Quasichemical Model considering the short-range ordering in molten oxide. While Al2TiO5 and Ti3O5 were treated as separate stoichiometric phases in the previous optimization, they were described in this study, using the Compound Energy Formalism, as part of pseudobrookite solid solution with a miscibility gap based on new experimental data. Corundum and rutile solutions were also described based on their crystal structures. New high temperature phase, Al6Ti2O13, was also considered for the first time. A set of optimized model parameters of all phases was obtained, which reproduces all available and reliable literature data within experimental error limits from 25°C to above the liquidus temperatures under oxygen partial pressures from metallic saturation to 1 atm. The newly optimized database was applied to calculate the inclusion diagram and reoxidation of Al-killed and Ti bearing steels.